VDSL packages are the same as ADSL packages really no difference whatsoever the prices are also the same as well, the only difference is that VDSL is designed for higher speeds than ADSL specifically the upload speeds so it can hold more than 1mbit upload speeds. With 8mbit you should get 2mbit upload with 12mbit you get 3mbit upload and with 16mbit you get 4mbit upload and so on. but with an ADSL copper line since the max upload speed is 1mbit, you won't see a difference in upload speed after 4mbit. with VDSl however, you'll be able to get that 2mbit upload along with 8mbit download same goes for the other packages.
Now the difference between MB(MegaByte) and Mb(Megabit). basically, B = Bytes and b = bits. now remember 8bits = 1Byte. the uppercase and lowercase Bs just makes it easier to tell them apart. Internet packages are in megabits. so an 8mbit package should theoretically give you 1MByte speed or 1024KByte in download speed. Most devices show the download rate in Bytes so don't get confused if you pay for 4mbit and get 512KByte.
Hope that clears your questions up a bit more and remember google is your friend